Endoparasite

Definition

A parasite that lives within the body of its host, typically in tissues, organs, or body cavities, rather than on the external surface. Endoparasites exploit host resources while remaining sheltered from environmental conditions and many host defenses. In entomology, this lifestyle is exemplified by strepsipterans (Strepsiptera), which develop inside the abdomens of host insects such as plant bugs (Hemiptera), bees, and wasps, with only adult males emerging to seek mates. The distinction from ectoparasite is functional rather than phylogenetic—endoparasites include protozoans, nematodes, and insect parasitoids that complete development internally.

Etymology

From Greek endon 'within' + parasitos 'one who eats at another's table'

Example

Strepsipteran males are the only free-living stage of these endoparasites; females remain as neotenic, legless forms inside the host, with only their cephalothoraces protruding between host abdominal segments to release larvae.

Synonyms

• internal parasite

Related Terms

• Ectoparasite
• endoparasitoid
• Parasitoid
• Host
• Parasitism
• mycetome
• bacteriocyte

Usage Notes

Contrast sharply with ectoparasite (external) and with endoparasitoid (which ultimately kills the host). The term describes habitat, not taxonomic affiliation—endoparasites span protozoans, helminths, fungi, and arthropods. In medical/veterinary entomology, mosquitoes and tsetse flies are vectors, not endoparasites themselves, though they may harbor endoparasitic protozoans (Plasmodium, Trypanosoma). Some specialists reserve 'endoparasite' for organisms that do not invariably kill the host, using 'endoparasitoid' for those that do, though usage varies.